Fungi turn leftovers from ethanol production into high-protein animal feed

An Iowa State University research group headed by engineering professor Hans van Leeuwen has developed a process where fungi are utilized to turn leftovers from ethanol production into high-protein animal feed1.

The process, named MycoMeal, use Rhizopus oligosporus – a fungus widely used as a starter culture for home-made soy patties (tempeh) in Indonesia.

In commercial ethanol production, roughly five gallons of leftovers in the form av stillage is formed for every gallon of ethanol produced. Stillage consists of solids and other organic material. Today, most of the stillage can be removed by centrifugation and dried to become livestock feed directly, but the but the remaining liquid – known as thin stillage – is more tricky to use and this is where MycoMeal comes into play.

The thin stillage contains some solids, plus a variety of organic compounds and enzymes. Roughly halft of the thin stillage can be recycled back into the ethanol production, but recycling more than that is not feasible since it would interfere with the ethanol production. The remaining thin stillage is instead evaporated and mixed with dried distillers grains.

What the Iowa State University research team has done is to add Rhizopus oligosporus to the thin stillage, where the fungi will produce fluffy, white mycelia – just as it does when you make tempeh from soy beans in your kitchen.

With the help of Rhizopus oligosporus, thin stillage can be turned into a thick cake-like mass within 24 hours. Most of the solids and roughly 60 percent of the organic material is removed by the fungi, making it easy to recycle the water and the enzymes back into the ethanol production. This makes ethanol production more efficient and less costly.

The “fungi-cake” can then be dried to form a high-protein animal feed rich in both essential amino acids and other valuable nutrients. There is even hope of using Rhizopus oligosporus to produce a low-cost nutritional supplement for humans at some point, but right now the research is focused on animal feed.

Fungi – the future of ethanol production?

Professor Van Leeuwen is far from the only researcher to link fungi to more efficient ethanol production. Around the globe, various types of fungi is being looked into by researcher either looking to produce ethanol directly or make the traditional process more efficient.

In one of his highly acclaimed green energy books “The Quest: Energy, Security and the Remaking of the Modern World “2, Pulitzer Prize winning energy-expert Daniel Yergin argues that energy security requires diversity of supply, and that genetically engineered ethanol-making fungi could be one of multiple routes to secure sufficient diversity within the energy producing field.

“Fortunately”, says Yergin, “there is growing availability of what may be the most important resource of all—human creativity.”